Flexible repetition of pusch mini-slots within a slot

ABSTRACT

The disclosure relates to a transmission device for transmitting data to a reception device in a communication system. The transmission device comprises circuitry which, in operation, allocates the data to a plurality of transmission time intervals, TTIs, respectively comprising a lower number of symbols than a slot and the plurality of TTIs including an initial TTI and one or more subsequent TTIs subsequent to the initial TTI, wherein the data allocated to each of the plurality of TTIs is the same, further allocates a demodulation reference signal, DMRS, to the initial TTI, and obtains a DMRS allocation for each of the subsequent TTIs indicating whether or not no DMRS is allocated to the respective TTI to be transmitted in addition to the data. The transmission device further comprises a transceiver which, in operation, transmits, within the slot, the data and DMRS in accordance with the DMRS allocation.

BACKGROUND Technical Field

The present disclosure relates to transmission and reception, devicesand methods in communication systems, such as 3GPP (3rd GenerationPartnership Project) communication systems.

Description of Related Art

Recently, the 3rd Generation Partnership Project (3GPP) concluded thefirst release (Release 15) of technical specifications for the nextgeneration cellular technology, which is also called fifth generation(5G). At the 3GPP Technical Specification Group (TSG) Radio Accessnetwork (RAN) meeting #71 (Gothenburg, March 2016), the first 5G studyitem, “Study on New Radio Access Technology” involving RAN1, RAN2, RAN3and RAN4 was approved and as a potential Release 15 work item thatdefines the first 5G standard. The aim of the study item is to develop a“New Radio (NR)” access technology, which operates in frequency rangesup to 100 GHz and supports a broad range of use cases, as defined duringthe RAN requirements study (see, e.g., 3GPP TR 38.913 “Study onScenarios and Requirements for Next Generation Access Technologies,”current version 14.3.0 available at www.3gpp.org).

The IMT-1010 (International Mobile Telecommunications-2020)specifications by the International Telecommunication Union broadlyclassified three major scenarios for next generation of mobilecommunications: enhanced Mobile Broadband (eMBB), massive Machine-typeCommunications (mMTC), and Ultra-Reliable and Low-Latency Communications(URLLC). In the recently completed 3GPP Release 15, the main focus wason standardizing the specifications for eMBB and some initial supportfor URLLC. For example, eMBB deployment scenarios may include indoorhotspot, dense urban, rural, urban macro and high speed; URLLCdeployment scenarios may include industrial control systems, mobilehealth care (remote monitoring, diagnosis and treatment), real timecontrol of vehicles, wide area monitoring and control systems for smartgrids; mMTC may include the scenarios with large number of devices withnon-time critical data transfers such as smart wearables and sensornetworks.

In Release 15, the scope of URLCC with respect to reliability includesspecification of new CQI (Channel Quality Indicator) and MCS (Modulationand Coding Scheme) table designs for target BLER of 1E-5, in addition tothe already agreed tables for target BLER of 1E-1. For URLLC, forgrant-based transmissions, one new RRC parameter is introduced forconfiguring a new RNTI (Radio Network Temporary Identifier). When thenew RNTI is not configured, existing RRC parameter “mcs-table” isextended to select from 3 MCS tables (existing 64QAM MCS table, existing256QAM MCS table, new 64QAM MCS table). When mcs-table indicates the new64QAM MCS table then for DCI format 0_0/1_0 in CSS (common searchspace), existing 64QAM MCS table is used, and for DCI formats0_0/1_0/0_1/1_1 in USS (user search space), the new 64QAM MCS table isused. Otherwise, existing behavior is followed. When the new RNTI (viaRRC, Radio Resource Control) is configured, RNTI scrambling of DCI CRCis used to choose MCS table. If the DCI CRC is scrambled with the newRNTI, the new 64QAM MCS table is used; otherwise, existing behavior isfollowed. The above configuration for DL (downlink) and UL (uplink) isseparate.

The scope of reliability of URLLC in Release 15 was quite limited.Therefore, in RAN #80, a new study item on physical layer enhancementsfor NR URLLC was approved (see. RP-181477, “New SID on Physical LayerEnhancements for NR URLLC,” Huawei, HiSilicon, Nokia, Nokia ShanghaiBell). In Release 15, the basic support for URLLC was introduced. For NRURLLC Rel. 16, further use cases with tighter requirements have beenidentified such as factory automation, transport industry and electricalpower distribution.

BRIEF SUMMARY

One non-limiting and exemplary embodiment facilitates providing flexibledemodulation reference signal configurations during repetition of datachannels.

In one general aspect, the techniques disclosed here feature atransmission device for transmitting data to a reception device in acommunication system. The transmission device comprises circuitry which,in operation, allocates the data to a plurality of transmission timeintervals, TTIs, respectively comprising a lower number of symbols thana slot and the plurality of TTIs including an initial TTI and one ormore subsequent TTIs subsequent to the initial TTI, wherein the dataallocated to each of the plurality of TTIs is the same, furtherallocates a demodulation reference signal, DMRS, to the initial TTI, andobtains a DMRS allocation for each of the subsequent TTIs indicatingwhether or not no DMRS is allocated to the respective TTI to betransmitted in addition to the data. The transmission device furthercomprises a transceiver which, in operation, transmits, within the slot,the data and DMRS allocated to the initial TTI and the data allocated tothe one or more subsequent TTIs to the reception device, wherein DMRStransmission in the one or more subsequent TTIs is performed inaccordance with the DMRS allocation.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic drawing of an exemplary architecture for a 3GPP NRsystem;

FIG. 2 is a block diagram of an exemplary user and control planearchitecture for the LTE eNB, NR gNB, and UE;

FIG. 3 is a schematic drawing showing usage scenarios of Massive MachineType Communications (mMTC) and Ultra Reliable and Low LatencyCommunications (URLLC)

FIG. 4 is a diagram of an example of inter-slot repetition of 2-symbolPUSCH (Physical Uplink Shared Channel);

FIG. 5 is an example of repetition of 4-symbol PUSCH within the sameslot;

FIG. 6 is a diagram of an example of 8-symbol PUSCH with one additionalDMRS (demodulation reference signal);

FIG. 7 is a diagram showing repetition with frequency hopping;

FIG. 8 is a diagram showing repetition with beam hopping;

FIG. 9 is a diagram showing an example of a repetition on measurementresources in a configured grant;

FIG. 10 is a diagram showing an example of two-symbol PUSCH transmissionwith 6 repetitions within a slot;

FIG. 11 is a block diagram of a transmission device and a receptiondevice;

FIG. 12 is a block diagram of a circuitry of a transmission device;

FIG. 13 is a flow chart of a transmission method and a reception method;

FIG. 14 is a diagram showing an example of removal of DMRS symbols fromcertain repetitions within a slot;

FIG. 15 is a diagram showing an example of replacement DMRS symbols bydata symbols in certain repetitions within a slot;

FIG. 16 is a diagram showing an example of a combination of removal andreplacement of DMRS symbols within a slot;

FIG. 17 is a flow chart of an uplink transmission method and an uplinkreception method

FIG. 18 is a graph showing exemplary control signaling of DMRSallocation

FIG. 19 is a diagram showing an example of repetition with frequencyhopping;

FIG. 20 is a diagram showing an example of repetition with beam hopping;

FIG. 21 is a diagram showing an example of repetition with repetition onmeasurement resources in a configured grant.

DETAILED DESCRIPTION

As presented in the background section, 3GPP is working at the nextreleases for the 5th generation cellular technology, simply called 5G,including the development of a new radio (NR) access technologyoperating in frequencies ranging up to 100 GHz. 3GPP has to identify anddevelop the technology components needed for successfully standardizingthe NR system timely satisfying both the urgent market needs and themore long-term requirements. In order to achieve this, evolutions of theradio interface as well as radio network architecture are considered inthe study item “New Radio Access Technology.” Results and agreements arecollected in the Technical Report TR 38.804 v14.0.0, incorporated hereinin its entirety by reference.

Among other things, there has been a provisional agreement on theoverall system architecture. The NG-RAN (Next Generation—Radio AccessNetwork) consists of gNBs, providing the NG-radio access user plane,SDAP/PDCP/RLC/MAC/PHY (Service Data Adaptation Protocol/Packet DataConvergence Protocol/Radio Link Control/Medium Access Control/Physical)and control plane, RRC (Radio Resource Control) protocol terminationstowards the UE. The NG-RAN architecture is illustrated in FIG. 1, basedon TS 38.300 v.15.0.0, section 4 incorporated herein by reference. ThegNBs are interconnected with each other by means of the Xn interface.The gNBs are also connected by means of the Next Generation (NG)interface to the NGC (Next Generation Core), more specifically to theAMF (Access and Mobility Management Function) (e.g., a particular coreentity performing the AMF) by means of the NG-C interface and to the UPF(User Plane Function) (e.g., a particular core entity performing theUPF) by means of the NG-U interface.

Various different deployment scenarios are currently being discussed forbeing supported, as reflected e.g., in 3GPP TR 38.801 v14.0.0, “Study onnew radio access technology: Radio access architecture and interfaces.”For instance, a non-centralized deployment scenario (section 5.2 of TR38.801; a centralized deployment is illustrated in section 5.4incorporated herein by reference) is presented therein, where basestations supporting the 5G NR can be deployed. FIG. 2 illustrates anexemplary non-centralized deployment scenario and is based on FIG.5.2.-1 of said TR 38.801, while additionally illustrating an LTE eNB aswell as a user equipment (UE) that is connected to both a gNB and an LTEeNB. As mentioned before, the new eNB for NR 5G may be exemplarilycalled gNB.

As also mentioned above, in 3rd generation partnership project new radio(3GPP NR), three use cases are being considered that have been envisagedto support wide variety of services and applications by IMT-2020 (seeRecommendation ITU-R M.2083: IMT Vision—“Framework and overallobjectives of the future development of IMT for 2020 and beyond,”September 2015). The specification for the phase 1 of enhancedmobile-broadband (eMBB) has been concluded by 3GPP in December 2017. Inaddition to further extending the eMBB support, the current and futurework would involve the standardization for ultra-reliable andlow-latency communications (URLLC) and massive machine-typecommunications. FIG. 3 (from the Recommendation ITU-R M.2083)illustrates some examples of envisioned usage scenarios for IMT for 2020and beyond.

The URLLC use case has stringent requirements for capabilities such asthroughput, latency and availability and has been envisioned as one ofthe enablers for future vertical applications such as wireless controlof industrial manufacturing or production processes, remote medicalsurgery, distribution automation in a smart grid, transportation safety,etc. In the current WID (work item description) RP-172115, it is agreedto support the ultra-reliability for URLLC by identifying the techniquesto meet the requirements set by TR 38.913.

For NR URLCC in Release 15, key requirements include a target user planelatency of 0.5 ms for UL (uplink) and 0.5 ms for DL (downlink). Thegeneral URLLC requirement for one transmission of a packet is a BLER(block error rate) 1E-5 for a packet size of 32 bytes with a user planeof 1 ms. From RAN perspective, reliability can be improved in a numberof possible ways. The current scope for improving the reliability iscaptured in RP-172817 that includes defining of separate CQI tables forURLLC, more compact DCI formats, repetition of PDCCH, etc. However, thescope may widen for achieving ultra-reliability as the NR becomes morestable and developed (for NR URLCC key requirements, see also 3GPP TR38.913 V15.0.0, “Study on Scenarios and Requirements for Next GenerationAccess Technologies” incorporated herein by reference). Accordingly, NRURLLC in Rel. 15 should be capable of transmitting 32 bytes of datapacket within a user-plane latency of 1 ms at the success probabilitycorresponding to a BLER of 1E-5. Particular use cases of NR URLCC inRel. 15 include Augmented Reality/Virtual Reality (AR/VR), e-health,e-safety, and mission-critical applications (see also ITU-R M.2083-0).

Moreover, technology enhancements targeted by NR URLCC in Release 15 aimat latency improvement and reliability improvement. Technologyenhancements for latency improvement include configurable numerology,non slot-based scheduling with flexible mapping, grant free (configuredgrant) uplink, slot-level repetition for data channels, and downlinkpre-emption. Pre-emption means that a transmission for which resourceshave already been allocated is stopped, and the already allocatedresources are used for another transmission that has been requestedlater, but has lower latency/higher priority requirements. Accordingly,the already granted transmission is pre-empted by a later transmission.Pre-emption is applicable independent of the particular service type.For example, a transmission for a service-type A (URLCC) may bepre-empted by a transmission for a service type B (such as eMBB).Technology enhancements with respect to reliability improvement includededicated CQI/MCS tables for the target BLER of 1E-5 (for the technologyenhancements, see also 3GPP TS 38.211 “NR; Physical channels andmodulation,” TS 38.212 “NR; Multiplexing and channel coding,” TS 38.213“NR; Physical layer procedures for control,” and TS 38.214 “NR; Physicallayer procedures for data,” respective versions V15.2.0, allincorporated herein by reference).

The use case of mMTC is characterized by a very large number ofconnected devices typically transmitting a relatively low volume ofnon-delay sensitive data. Devices are required to be low cost and tohave a very long battery life. From NR perspective, utilizing verynarrow bandwidth parts is one possible solution to have power savingfrom UE perspective and enable long battery life.

As mentioned above, it is expected that the scope of reliability in NRbecomes wider. One key requirement to all the cases and especiallynecessary for URLLC and mMTC is high reliability or ultra-reliability.Several mechanisms can be considered to improve the reliability fromradio perspective and network perspective. In general, there are few keypotential areas that can help improve the reliability. Among these areasare compact control channel information, data/control channelrepetition, and diversity with respect to frequency, time and/or thespatial domain. These areas are applicable to reliability in general,regardless of particular communication scenarios.

For NR URLLC Rel. 16, further use cases with tighter requirements havebeen identified such as factory automation, transport industry andelectrical power distribution, including factory automation, transportindustry, and electrical power distribution (see RP-181477, “New SID onPhysical Layer Enhancements for NR URLLC,” Huawei, HiSilicon, Nokia,Nokia Shanghai Bell, incorporated herein by reference). The tighterrequirements are higher reliability (up to 10-6 level), higheravailability, packet sizes of up to 256 bytes, time synchronization downto the order of a few μs where the value can be one or a few μsdepending on frequency range and short latency in the order of 0.5 to 1ms in particular a target user plane latency of 0.5 ms, depending on theuse cases (see also 3GPP TS 22.261 “Service requirements for nextgeneration new services and markets” V16.4.0, incorporated herein byreference and RP-181477).

Moreover, for NR URLCC in Rel. 16, several technology enhancements fromRAN1 perspective have been identified. Among these are PDCCH (PhysicalDownlink Control Channel) enhancements related to compact DCI, PDCCHrepetition, increased PDCCH monitoring. Moreover, UCI (Uplink ControlInformation) enhancements are related to enhanced HARQ (Hybrid AutomaticRepeat Request) and CSI feedback enhancements. Also PUSCH enhancementsrelated to mini-slot level hopping and retransmission/repetitionenhancements have been identified. The term “mini-slot” refers to aTransmission Time Interval (TTI) including a smaller number of symbolsthan a slot (a slot comprising fourteen symbols).

In general, TTI determines the timing granularity for schedulingassignment. One TTI is the time interval in which given signals ismapped to the physical layer. Conventionally, the TTI length can varyfrom 14-symbols (slot-based scheduling) to 2-symbols (non-slot basedscheduling). Downlink and uplink transmissions are specified to beorganized into frames (10 ms duration) consisting of 10 subframes (1 msduration). In slot-based transmission, a subframe, in return, is dividedinto slots, the number of slots being defined by thenumerology/subcarrier spacing and the specified values range between 10slots for a subcarrier spacing of 15 kHz to 320 slots for a subcarrierspacing of 240 kHz. The number of OFDM symbols per slot is 14 for normalcyclic prefix and 12 for extended cyclic prefix (see section 4.1(general frame structure), 4.2 (Numerologies), 4.3.1 (frames andsubframes) and 4.3.2 (slots) of the 3GPP TS 38.211 V15.0.0 (2017-12)incorporated herein by reference). However, assignment of time resourcesfor transmission may also be non-slot based. In particular, the TTIs innon slot-based assignment may correspond to mini-slots rather thanslots. I.e., one or more mini-slots may be assign to a requestedtransmission of data/control signaling. In non slot-based assignment,the minimum length of a TTI may conventionally be 2 OFDM symbols.

Other identified enhancements are related to scheduling/HARQ/CSIprocessing timeline and to UL inter-UE Tx prioritization/multiplexing.Further identified are UL configured grant (grant free) transmissions,with focus on improved configured grant operation, example methods suchas explicit HARQ-ACK, ensuring K repetitions and mini-slot repetitionswithin a slot, and other MIMO (Multiple Input, Multiple Output) relatedenhancements (see also 3GPP TS 22.261 V16.4.0).

The present disclosure is related to the potential layer 1 enhancementsfor further improved reliability/latency and for other requirementsrelated to the use cases identified in (RP-181477, “New SID on PhysicalLayer Enhancements for NR URLLC,” Huawei, HiSilicon, Nokia, NokiaShanghai Bell). Specifically, enhancements for PUSCH (Physical UplinkShared CHannel) repetition are discussed. The impact of the proposedideas in this disclosure is expected to be on PUSCH repetitionenhancements which is within the main scope of new SI (study items)/WI(work items) on NR URLLC in Rel. 16.

PUSCH Repetition

One of the scopes for potential enhancements is related to mini-slotrepetition of PUSCH within slot. In the following, a motivation forsupporting repetition of PUSCH within a slot which may allow forpotential enhancements to the repetition mechanism for further improvingthe reliability and/or latency to satisfy the new requirements of NRURLLC, is provided.

To achieve the latency requirement for URLLC PUSCH transmission,one-shot transmission (i.e., single (TTI) assignment) is ideal, providedthe reliability requirement is satisfied. However, it is not always thecase that the target BLER of 1E-5 is achieved with one-shottransmission. Therefore, retransmission or repetition mechanisms arerequired. In NR Rel.15, both retransmissions and repetitions aresupported to achieve the target BLER, when one-shot transmission is notenough. HARQ-based retransmission is well known to improve the overallreliability, by using the feedback information and improving thesubsequent retransmissions according to the channel conditions. However,they suffer from additional delay due to feedback processing timeline.Therefore, repetitions are useful for highly delay-tolerant services, asthey do subsequent transmission of the same data packet without waitingfor any feedback.

A PUSCH repetition can be defined as “transmitting the same uplink datapacket more than once, without waiting for any feedback of previoustransmission(s) of the same data packet.” Advantages of PUSCretransmissions are an improvement in the overall reliability and areduction in latency in comparison with HARQ, as no feedback isrequired. However, in general, no link adaptation is possible, andresource usage may be inefficient.

In NR Rel. 15, limited support for repetition is introduced. Onlysemi-static configuration of repetition is allowed. Moreover, repetitionis allowed only between slots as shown in FIG. 4 (slot level PUSCHrepetition). I.e., repetition is only possible in the slot following theslot of the previous transmission. Depending up on the numerology andservice type (e.g., URLCC, eMBB), latency between the repetitions can betoo long for inter-slot repetition. Such type of repetition is mainlyuseful for PUSCH mapping type A that allow the PUSCH transmission tostart only from the beginning of the slot. Such limited support may notbe able to achieve stricter latency requirements in NR Rel. 15 i.e., upto 0.5 ms latency. Therefore, repetition of PUSCH within the slot isbeing considered for NR URLLC in Rel. 16.

Repetition within the same slot can be supported for PUSCH mapping typeB that allows the scheduling of a given transmission (or repetition fromany symbol of the slot in contrast to only beginning of the slot inPUSCH mapping type A). For example, two repetitions can be scheduledadjacently within the slot as shown in FIG. 5, which provides even lowerlatency between repetitions in comparison to inter-slot repetition. Inthe figure, a single transmission consists of 1 DMRS and 3 data symbols,which is followed by exact same repetition.

However, it can be argued that the exact same configuration is achievedby even single transmission without repetition. Basically, the length ofinitial transmission is longer and additional DMRS symbol is configured,which is supported in NR Rel. 15, as shown in FIG. 6, with an additionalDMRS in allocated to the fifth symbol of the slot. In the example shownin FIG. 6, a single transmission consists of 1 front-loaded DMRS+1additional DMRS configuration and 6 data symbols which is practicallysame as repetition case.

Accordingly, supporting repetition within the same slot may beconsidered to provide the same functionality that can be achieved bysingle transmission with longer TTI (Transmission Time Interval) length.Therefore, to support and specify repetition of PUSCH within the slots,better functionalities with more flexibility and gains should berealized that cannot be achieved by existing support for PUSCHtransmission.

Accordingly, it is desirable to improve mini-slot repetition within aslot to achieve more flexibility and gains that cannot be achieved bysingle assignment. It is therefore a proposal of the present disclosurethat for PUSCH mapping type B, repetition of PUSCH within the same slotshould be supported, only if additional functionalities with moreflexibility and gains are realized in comparison with existing supportfor PUSCH transmission.

Repetition within a slot as such seems to provide similar functionalityas single assignment. However, if it is combined with the other existingphysical layer techniques, more flexibility with better gains could beachieved. Discussed below are some possible use-cases that could beachieved only if repetition within the slot is supported.

For PUSCH mapping type B, frequency diversity gains can be furtherexploited if frequency hopping between repetitions is allowed within aslot. It would give the flexibility to schedule each repetition on twoor more hops depending up on the size of the bandwidth part, as shown inFIG. 7. Basically, more configurations could be possible in comparisonto single transmission within a slot. Inter-frequency hopping may referto hopping between subcarrier blocks comprising e.g., 12 subcarriers(corresponding to a Resource Block size in the frequency domain).However, frequency hopping may also refer to bandwidth part hopping. Inaccordance with section 4.4.5 of TS 38.211 V15.0.0 (2017-12), abandwidth part (or carrier bandwidth part) is a contiguous set ofphysical resource blocks as defined in clause 4.4.4.3, selected from acontiguous subset of the common resource blocks defined in clause4.4.4.2 for a given numerology on a given carrier.

Another benefit of using repetition within a slot is that eachrepetition can be transmitted on a different beam to achieve morespatial diversity gain which is not possible in case of singletransmission, as shown in FIG. 8. Beamforming allows to concentrate theenergy of a given radio transmission in a certain direction, such thatthe range can be extended to, for instance, compensate the highpropagation loss in high frequencies. For example, if singletransmission and 3 repetitions are allowed within a slot, then up tofour different beams can be utilized for each transmission and thusattaining more spatial diversity and potentially improved reliability.

In configured grant (also known as grant-free) PUSCH, all the allocatedresources to PUSCH may or may not belong to uplink. Only the symbolsthat are indicated as UL could be used. Therefore, it may happen thatthe number of UL indicated symbols are not enough or contiguous to allowthe transmission of longer PUSCH. Therefore, shorter PUSCH can be moreefficiently scheduled and its repetition within the slot can utilize thenon-contiguous symbols available for uplink, as shown in FIG. 9.

It is an observation of the present disclosure that for PUSCH mappingtype B, repetition within the slot (i.e., a whole sequence of an initialtransmission and repetitions performed in a single slot) can providebetter flexibility and gains in combination with other physical layertechniques such as frequency hopping and beam hopping by exploitingfrequency diversity and spatial diversity, respectively. Moreover, it isobserved that for PUSCH mapping type B with configured grant, repetitionwithin the slot allows to efficiently use measurement resources with asmall number of UL symbols.

In conventional repetitions, the same transport block (TB) istransmitted in the initial transmission and all the repetition roundsalong with same DMRS configuration. However, this might lead tosub-optimality in terms of DMRS overhead. For example, as shown in FIG.10, in case of 2-symbol PUSCH with initial transmission and 6repetitions, the DMRS overhead is 50%, which is very high. For everyrepetition round, the mini-slot consists of one data and DMRS symbols ina respective TTI, which is very inefficient in terms of resource usageas DMRS symbols are very frequent over the period of slot within whichall of the initial transmission and the repetitions are performed.

Thus, it is observed that conventional repetition can lead to very highDMRS overhead in certain scenarios where the length of PUSCH is quiteshort. In other words, every repetition round corresponding to one ofthe subsequent TTIs/mini-slots consists of one data and DMRS symbols,which is very inefficient in terms of resource usage as DMRS symbols arevery frequent over the period of slot. Accordingly, it is desirable toimprove mini-slot repetition within a slot to improve latency and/orreliability in comparison with the conventional repetition mechanism.

On the other hand, even for high mobility UEs (i.e., UEs moving withhigh speed and therefore requiring frequent adaptation to rapidlychanging channel characteristics), such high density of DMRS is notalways required.

In view of the above observations and considerations, the disclosureproposes to allow, in mini-slot repetition of data within a slot, tochange or vary DMRS allocation/DMRS symbol(s) allocation in at least oneof the repetitions which is configured by a signaling mechanism. To thisend, proposed transmission and reception devices and methods aredescribed in the following aspects and embodiments of the disclosure.

It should be noted that the above motivation has made reference to thecontext of PUSCH repetitions and further referred to NR URLCC as aservice type, the present disclosure is not limited to a particularservice type or communication channel/link. In particular, as will beshown in the following description, the present disclosure is applicableto the uplink as well as the downlink case.

In general, this disclosure provides a transmission device 1110 fortransmitting data to a reception device 1160 over a channel (e.g., awireless channel) in a communication system, particularly a wirelesscommunication system. The transmission device 1110 shown in FIG. 11comprises processing circuitry 1130 and a transceiver 1120. Theprocessing circuitry, in operation, allocates the data to a plurality oftransmission time intervals, TTIs. The plurality of TTIs respectivelycomprise a lower number of symbols than a slot. Therein, the dataallocated to each of the plurality of TTIs is the same. In addition tothe data, a demodulation reference signal (DMRS) is allocated to aninitial TTI among the plurality of TTIs. Moreover, the circuitry 1130,in operation obtains a DMRS allocation for each of the subsequent TTIsof the plurality of TTIs which are subsequent to the initial TTIs,indicating whether or not no DMRS is allocated to the respective TTI. Inthis disclosure, devices or device parts adapted or configured toperform a given task are said to, “in operation,” perform the giventask. In accordance with the operation described, as shown in FIG. 12,the processing circuitry 1130 comprises a DMRS allocation unit obtainingunit 1231 which, in operation, obtains the DMRS allocation, andDMRS/data allocation unit which allocates data to the plurality of TTIs,allocates a DMRS to the initial TTI and allocates DMRS or no DMRS to thesubsequent TTIs in accordance with the DMRS allocation obtained by theDMRS allocation obtaining unit 1231.

The DMRS allocation is an allocation scheme or allocation configurationwhich indicates for a TTI whether or not no DMRS is allocated to therespective TTI. I.e., the DMRS allocation indicates whether a DMRS isallocated to a TTI or not, to be transmitted in the respective TTI inaddition to the data. Accordingly, if a DMRS allocation for one of thesubsequent TTIs indicates that a DMRS is to be transmitted in therespective subsequent TTI, a DMRS is allocated to the TTI. However, ifthe DMRS allocation indicates that no DMRS is to be transmitted in therespective TTI, no DMRS is allocated to the TTI.

The transceiver 1120 (i.e., a transmitter and receiver, meaning hardwareand software components of a transmission and or reception deviceadapted to transmit/receive a radio signal and modulate/demodulate dataallocated to time and frequency resources of the radio signal) of thetransmission device, in operation transmits within the slot, the dataallocated to the plurality of TTIs to the reception device. Moreover,the transceiver 1120 transmits, in the initial TTI, the DMRS allocatedto the initial TTI, and performs DMRS transmission in the one or moresubsequent TTIs in accordance with the obtained DMRS allocation. I.e.,on the one hand, in a subsequent TTI to which a DMRS is allocated, theDMRS and data are transmitted. On the other hand, in a subsequent TTI towhich no DMRS is allocated, the data is transmitted, withouttransmitting a DMRS.

This disclosure further provides a reception device 1160 for receiving,from a transmission device 1110 over a channel (e.g., a wirelesschannel) in a communication system such as a wireless system, data. Thereception device 1160 comprises circuitry 1189 and a transceiver 1170.The circuitry 1180 of the reception device, in operation, obtains a DMRSallocation, for each of one or more subsequent TTIs, i.e., TTIssubsequent to an initial TTI, subsequent TTIs and initial TTI beingcomprised by a plurality of TTIs respectively having a lower number ofsymbols than a slot. The data allocated each of the plurality of TTIs isthe same. In accordance with the above description, the DMRS allocationfor a TTI indicates whether or not no DMRS is allocated to therespective TTI to be received in addition to the data. The transceiver1170 of the reception device 1160, in operation, receives, within theslot, the data and DMRS allocated to the initial TTI and the dataallocated to the one or more subsequent TTIs from the transmissiondevice, wherein DMRS reception in the one or more subsequent TTIs isperformed in accordance with the DMRS allocation.

In correspondence with the above-describe transmission device 1110 andreception device, provided are a transmission method and respectively, areception method shown in FIG. 13. Both the transmission method and thereception method comprise a step of obtaining S1310, S1360, ademodulation reference signal, DMRS, allocation for each of one or moresubsequent TTIs subsequent to an initial TTI. The DMRS allocationindicates whether or not no DMRS is allocated to the respective TTI tobe transmitted in addition to the data, wherein a plurality of TTIsincluding the initial TTI and the one or more subsequent TTIsrespectively comprise a lower number of symbols than a slot. Thetransmission method further comprises the allocation step S1320 ofallocating the same data to each of the plurality of TTIs, allocating aDMRS to the initial TTI and, if indicated by the DMRS allocation,allocating DMRS to one or more of the subsequent TTIs. The transmissionmethod further comprises a transmission step S1330 of transmitting thedata and DMRS allocated to the initial TTI and the data allocated to theone or more subsequent TTIs to the reception device, wherein DMRStransmission in the one or more subsequent TTIs is performed inaccordance with the DMRS allocation. The reception method comprises thestep S1370 of receiving, within the slot, the data and DMRS allocated tothe initial TTI and the data allocated to the one or more subsequentTTIs from the transmission device, wherein DMRS reception in the one ormore subsequent TTIs is performed in accordance with the DMRSallocation.

As described above, data and possibly reference signal are allocatedrespectively to transmission time intervals (TTIs) which arerespectively smaller than a slot. Accordingly, the present disclosureparticularly relates to non slot-based assignment described above. Asmentioned, in non slot-based assignment, the minimum length of a TTI mayconventionally be 2 OFDM symbols. Such two-symbol TTIs are shown in FIG.10. The TTIs, which are smaller than a slot, are referred to in thisdisclosure as mini-slots, without limiting the disclosure to suchterminology. In particular, due to the small size of the mini-slotsTTIs, a complete sequence of repetitions including the initialtransmission in the first two symbols (i.e., a DMRS symbol and a datasymbol) and six repetition also respectively including a DMRS symbol anda data symbol fit into the slot, so that the whole series of repetitionsis made within a single slot. Moreover, the present disclosure providesfor TTIs to which no DMRS is assigned, i.e., TTIs that do not include aDMRS symbol. Accordingly, if a DMRS symbol is removed from a mini-slothaving only one data symbol, the minimum size of the TTI will be onesymbol rather than the two-symbols conventionally assumed.

Within a TTI/mini-slot to which a DMRS is allocated, a symbol to which aDMRS is allocated (DMRS) symbol precedes one or more symbols on whichthe data is transmitted. The DMRS is used on the receiver side forchannel estimation for coherent demodulation. In general, it is alsopossible that a TTI comprises more than one DMRS symbol for DMRSretransmission preceding the data symbol(s) in which the data aretransmitted.

However, in scenarios where the channel characteristics are not expectedto change during the duration of one or two minis-slots in a manner thatcoherent demodulation is impaired, it may be sufficient to allocate aDMRS symbol to a first TTI prior to one or more subsequent TTIs, but notallocate any DMRS to the subsequent TTIs. I.e., in such a case, no DMRSis transmitted in at least one of the one or more subsequentTTIs/mini-slots subsequent to the initial TTI. Such non-allocation ofDMRS to subsequent TTIs within a slot may be performed for example inuse cases where transmission devices are expected to be non-moving ormoving with low speed, such as factory automation.

An example of a flexible DMRS allocation for data repetitions is shownin FIG. 14. The figure shows a slot including 14 symbols, the first tensymbols of which are occupied by a series of initial transmission andrepetitions. An initial transmission in an initial mini-slot correspondsto the first two symbols and is followed by six data repetitions in sixsubsequent TTIs. In the first and fourth repetition, further DMRS aretransmitted, i.e., the first and fourth subsequent mini-slots bothcomprise a DMRS symbol in addition to a data symbol. Accordingly, theDMRS allocation of the first and fourth subsequent TTI indicaterespectively indicate that a DMRS is to be transmitted in these TTIs. Onthe other hand, according to the respective DMRS allocations of the TTIscorresponding to the second, third, fifth, and sixth repetitions, noDMRS is allocated to any of the latter TTIs.

A benefit of the transmission/reception devices and methods of thepresent disclosure is that flexible allocation and non-allocation ofDMRS to mini-slots, such as flexible removal and/or replacement of DMRSwith one or more data repetitions to be explained in the following, mayallow configurations with more gain that are not possible with singleassignment (i.e., the same DMRS allocation for each TTI of a repetition)due to limited existing DMRS configurations.

As has been described, the DMRS allocation scheme for a mini-slot, i.e.,a TTI having less symbols than a slot, indicates or specifies whether ornot a DMRS is allocated to a mini-slot, in particular to one or moresymbols of the mini-slot (which generally include the first symbol intime order). A DMRS allocation is therefore also called a DMRS symbol(s)allocation in this disclosure. In the following, more details onpossible DMRS symbol allocations will be provided. In particular, itwill be described how data is allocated to the respective symbols ofTTIs within a slot if the DMRS symbol allocation for at least one TTIwithin a slot specifies that no DMRS is allocated to the TTI.

So far, it has been described that in a series of DMRS repetitions inmini-slots within one slot, no DMRS is allocated to certain TTIs inwhich data repetitions are performed. In particular, flexible DMRSallocation or changing DMRS symbol(s) allocation according to someembodiments of the present disclosure may mean the following:

-   -   The DMRS symbol(s) in a given repetition is (are) removed, and        only the data symbols(s) are transmitted in the respective TTI        corresponding to the given repetition. Flexible removal of DMRS        symbol(s) in one or more repetition(s) may facilitate reducing        the latency to achieve a final target BLER in comparison with        conventional repetition (i.e., repetition where a DMRS is        allocated to each TTI in which a repetition is made).    -   The DMRS symbol(s) in a given repetition is (are) replaced with        a data symbol(s), and the Transport Block (TB) corresponding to        the data to be transmitted is sent with a reduced coding rate        relative to the initial transmission. Flexible replacement of        DMRS symbols(s) in one or more repetition may facilitate        increasing the reliability in comparison with conventional        repetition.    -   Removal and replacement of DMRS symbol(s) are combined. This may        facilitate providing both latency and reliability improvements        in comparison with conventional repetition.

Removal of DMRS

According to some embodiments, the DMRS allocation further indicatesthat if no DMRS is allocated to the respective TTI, a length of therespective TTI is reduced by one (or more) symbol(s) corresponding tothe DMRS. That means, in the TTIs to which no DMRS is allocated, theDMRS symbol (or DMRS symbols) is removed.

Accordingly, one possible enhancement to conventional repetition is toallow the flexibility to remove DMRS from certain repetitions dependingup on the channel conditions and reliability requirements. As anexample, if it is allowed to remove DMRS from certain repetitions incase of 2-symbol PUSCH with initial transmission and 6 repetitions, oneof the possibility could look like the above described allocation ofdata and DMRS to TTIs shown in FIG. 14. This flexibility will not onlyallow to control the DMRS overhead, but additionally give moreflexibility in terms of DMRS configurations that are currently notsupported in NR Rel. 15. Furthermore, the overall latency is alsoreduced by allowing such flexibility.

The repetition rounds without the DMRS corresponding to mini-slots/TTIswithout DMRS symbol will use the last available DMRS for channelestimates. In particular, 2nd and 3rd repetitions are without DMRS andthey use DMRS from the 1st repetition for demodulation. Similarly, 5thand 6th repetition are without DMRS and they use DMRS from the 4threpetition for demodulation.

In terms of demodulation performance, there should be negligibledifference for the repetitions without the DMRS, in particular inapplications with low mobility requirements for transmitting devicessuch as UEs, because the distance with the last available DMRS from theprevious repetitions is still rather low. Moreover, in the initial datatransmission as well as in each of the repetition rounds, the same MCS(modulation and coding scheme), in particular the same coding rate, maybe used because the same amount of data symbols is available in theinitial TTI as well as in each of the one or more subsequent TTIs, e.g.,one data symbol per transmission.

Such a configuration, in particular data/DMRS allocation to symbolswithin one slot, is not possible according to currently supported DMRSconfigurations for single assignment. For such a configuration, theperformance may be similar or improved in comparison with the currentconfigurations for single transmission.

Furthermore, in comparison with conventional repetition, the samereliability can be achieved with a reduction in latency. For instance,as shown in FIG. 14, the latency is reduced by four symbols.

Moreover, resources, in particular resources of the time domain, can besaved with respect to conventional repetition. While for conventionalrepetition, all fourteen symbols of a slot are consumed for a series ofan initial transmission and six repetitions, according to the currentembodiment, some symbols in a slot may be unused by the series ofinitial transmission and repetitions (e.g., the four last symbols of theslot shown in FIG. 14) and can be used for other transmissions, forexample other URLLC traffic in the queue for same or other UEs.

Accordingly, with particular respect to PUSCH mapping type B mentionedabove, it is a further observation of the present disclosure that forrepetition within the slot for PUSCH mapping type B, removal of DMRSfrom certain repetition rounds will allow to reduce the DMRS overheadand provide more flexibility in terms of DMRS configurations, which arenot possible currently in NR Rel. 15. An additional observation is thatfor repetition within the slot for PUSCH mapping type B, removal of DMRSfrom certain repetition rounds will also allow to reduce the overalllatency and make the resources available for other traffic in thepipeline, e.g., URLLC/eMBB. Accordingly, possible latency improvementsmay further be advantageous in view of pre-emption discussed above. Adelay of a transmission pre-empted by a sequence of repetition may bereduced along with the latency.

Replacement of DMRS

According to some embodiments, the DMRS allocation for a TTI from amongthe one or more subsequent TTIs further indicates that if no DMRS isallocated to respective TTI smaller than a slot, a symbol for allocationof the DMRS in the respective TTI is replaced by a symbol for allocationof the data. In other words, in a mini-slot, a DMRS symbol is replacedby a data symbol.

An exemplary allocation of DMRS and data to symbols of TTIs within aslot where DMRS symbols are replaced by data symbols is shown in FIG.15. The slot comprises seven mini-slots each comprising two symbols. Thefirst (initial) mini-slot in which the initial PUSCH transmission isperformed as well as the subsequent TTIs on which the data for thefirst, third and fifth repetition are allocated respectively comprise aDMRS symbol and a data symbol. However, the second, fourth, and sixthrepetitions are respectively without data symbol. In the TTIscorresponding to these repetitions, the DMRS are respectively replacedwith data symbols. Thus, each of the second, fourth and sixth subsequentmini-slot includes two data symbol than one data symbol preceded by aDMRS symbol.

With a DMRS allocation scheme for repetitions within a slot, a principlecan be applied to reduce the MCS (i.e., the coding rate) in certainrepetitions to improve the coding gain, while at the same time keepingdesired demodulation performance by preventing the distance between datasymbols and DMRS from being long. As can be seen from FIG. 15, when aDMRS symbol is replaced by a data symbol in a TTI having two symbols,the number of symbols available for transmission is doubled. Moreover,the same data are transmitted in each repetition. Accordingly, in thetwo-symbol example, the coding rate can basically be reduced to half thecoding rate of the initial data transmission in all repetitions wherethe changes, i.e., the replacement of a DMRS symbol by a data symbol,apply. However, as the present disclosure is not limited to a TTI havingtwo symbols, the decreased coding rate may also take other values thanhalf of the original coding rate by which the data is coded in theinitial TTI and the subsequent TTIs including DMRS symbols.

In comparison with single assignment where such configurations asexemplified by FIG. 15 are not possible according to current DMRSconfigurations, a configuration where DMRS symbols are replaced by datasymbols, a similar or even better performance may be obtained. Moreover,in comparison to conventional repetition, the reliability may further beimproved while keeping the latency the same.

As has been described above, DMRS symbols may be removed or replacedfrom certain TTIs within a slot. For instance, within a single slot or asequence of slots, the change in the DMRS symbol(s) allocation may berestricted either to removal of DMRS symbols or replacement of DMRSsymbols. I.e., within such slots, if no DMRS is allocated to one moresubsequent TTIs, only removal is performed, or only replacement isperformed. However, as will be described in the following embodiments,removal and replacement of DMRS symbols may also be combined withrespect to different TTIs within a single slot.

Combination of Removal and Replacement

For instance, according to some embodiments, the DMRS allocation furtherindicates that if no DMRS is allocated to the respective TTI, either alength of the respective TTI is reduced by one symbol corresponding tothe DMRS (removal of DMRS symbol) or a symbol for allocation of the DMRSin the respective TTI is replaced by a symbol for allocation of the data(replacement of DMRS symbol). Accordingly, among the one or moresubsequent TTIs on which the data is to be transmitted repeatedly withina slot, a configuration is possible DMRS symbol removal is applied toone of the subsequent TTIs, whereas DMRS symbol replacement is appliedto another one of the subsequent TTIs, irrespective of the order ofthese TTIs in time direction. i.e., a TTI in which the DMRS symbol isremoved may precede a TTI in which the DMRS symbol is replaced intransmission order, or vice versa.

A slot in which both removal and replacement of DMRS symbols areperformed in different TTIs included in the slot is shown in FIG. 16. Inparticular, the second and fifth subsequent mini-slots in which thesecond and fifth repetitions are performed, are without DMRS symbol, andthe length of these mini-slots is reduced accordingly. The third andsixth subsequent mini-slots corresponding to the third and sixthrepetitions, are without DMRS symbol as well, wherein the DMRS symbol isreplaced by a further data symbol. In the third and sixth repetitionswith respectively two data symbols, the code made may be reduced tohalf, as described above. Moreover, as can be further be seen, the lasttwo symbols of the slot in time order are unused for the sequence ofinitial transmission and repetitions and thus available for othertraffic in the pipeline.

Such a hybrid use of DMRS symbol removal and DMRS symbol replacement bydata symbols may facilitate increasing the reliability and at the sametime reduce the latency with respect to conventional repetitions. Whileremoval of DMRS symbols may provide latency improvements, whereasreplacement of DMRS symbols accompanied by a reduction of the codingrate may facilitate increasing the reliability, a combination of theseembodiments provides greater flexibility and allows for tradeoffsbetween the different aims.

As has been mentioned, in some embodiments, if a symbol for allocationof the DMRS in the respective TTI is replaced by a symbol for allocationof the data, the data is transmitted in the respective TTI with a coderate lower than a code rate (or coding rate) by which the data istransmitted in the initial TT. For instance, as shown, the lower coderate may be half the code rate by which the data transmitted in theinitial TTI/mini-slot is coded, but the disclosure is not limited toreducing the coding rate by one half. Alternatively, if the initial TTIcomprises two data symbols and one DMRS symbol and a subsequent TTI hasthree data symbols and no DMRS symbol, the coding rate may be reduced totwo thirds of the coding rate used in the initial transmission. As hasbeen described, the mentioned reductions in the coding rate are to beunderstood as relative to the coding rate of the data in the initial TTIrather than a reduction of an absolute coding rate 1 to e.g., 1/2. i.e.,the described decrease in the coding rate is independent from theoriginal value of the coding rate.

Uplink Transmission and Repetitions

Some examples have been shown in which a sequence of initialtransmission and repetitions constitute uplink transmissions, such asPUSCH (physical uplink shared channel) transmissions. Accordingly, insome embodiments, the transmission device 1110 (in particular thetransceiver 1120 of the transmission device 1110 in operation) transmitsthe data to the reception device on an uplink, and the transceiver 1120of the transmission device 1110 further receives from the receptiondevice 1160 control signaling. Correspondingly, the reception device1160 transmits the control signaling to the transmission device.

The control signaling includes an allocation indicator for each of thesubsequent TTIs indicating the respective DMRS allocation. The circuitry1130 of the transmission device, obtains the DMRS allocation for each ofthe TTIs subsequent to the initial TTI by evaluating the controlsignaling.

In embodiments where the transmission device 1110 transmits the data tothe reception device 1160 on the uplink, the transmission device may bea terminal or user equipment, the reception device 1160 may be may be abase station which is referred to in NR (New Radio) communicationsystems as gNB or gNodeB in correspondence with the eNodeB (eNB) of LTE(Long Term Evolution) or LTE-Advanced systems. The data transmission onthe uplink may correspond to an initial PUSCH transmission and one ormore repetitions.

An uplink transmission method and an uplink reception method accordingto the present disclosure are shown in FIG. 17. As shown a gNBcorresponding to the reception device 1160 obtains the DMRS by adetermination step S1760 of determining the DMRS allocation (embodyingstep S1360 of FIG. 13). In particular, such a determination of a DMRSallocation is performed based on channel quality estimation. Inparticular, the base station may estimate the channel quality based onuplink sounding reference signals (SRS) which UEs transmit for thepurpose of channel quality estimation. The gNB may receive SRS from oneor more UEs and determine the DMRS allocation based on the channelconditions corresponding to the channel quality estimated based on thereceived SRS.

The gNB/base station then generates a DMRS allocation indicator andtransmits, in step S1765, the control signaling including the allocationindicator to the (user) terminal. The user terminal receives the controlsignaling including the DMRS allocation indicator in step S1710(embodying step S1210 of FIG. 13) and thereby obtains the DMRSallocation. The allocation step S1320 and the transmission step S1330 ofthe uplink transmission method and the reception step S1370 of theuplink reception method are performed in accordance with thecorresponding general methods shown in FIG. 13.

Control Signaling

In particular, in some embodiments, the DMRS allocator for each of theone or more subsequent TTIs is a two-bit allocation indicator. Two bitsare sufficient to indicate whether or not no DMRS is allocated to theTTI and to further indicate which of the options removal of the DMRS orreplacement of the DMRS is applied. Accordingly, each repetition may berespectively associated with one of two bits of the followingindication.

-   -   ‘00’: no change to DMRS symbol(s) in a given repetition (i.e.,        DMRS is allocated to the TTI)    -   ‘01’: DMRS symbol(s) to be removed and the TTI length of given        repetition is reduced    -   ‘10’: DMRS symbol(s) to be replaced with data symbol(s) and the        coding rate of the given repetition is reduced    -   ‘11’: reserved entry

In accordance with the above two-bit indication, a DMRS allocationindicator for six repetitions consists of six two-bit indicators. Forthe example of the combination of removal and replacement of DMRSsymbols shown in FIG. 16, the resulting twelve-bit indicator reads “0001 10 00 01 10.” This indicator is also shown in FIG. 18.

Clearly, the association between two-bit values and DMRS allocations ismerely exemplary. Alternatively, for instance, ‘10’ may denote DMRSsymbol(s) removal.

Alternatively, the DMRS allocation indicator may have more or less thantwo bits. In particular, the DMRS allocation indicator for each of thesubsequent TTIs to be transmitted within a slot may be a one-bitindicator, resulting in a six-bit field for the indication of DMRSallocations of a maximum of six retransmissions. A one-bit indicatorcorresponding to a TTI is sufficient to indicate whether or not a DMRSis allocated to the respective TTI, provided it is clear or known, forexample from a standard or from further control signaling, whatparticular modifications are made to the allocation in the TTI, e.g.,whether removal or replacement of the DMRS symbol is performed. Forinstance, a bit value of “0” may indicate that a DMRS is allocated toand transmitted in the respective TTI, and “1” may indicate that no DMRSis allocated, irrespective of whether the DMRS symbol is replaced orremoved. Accordingly, the resulting six-bit DMRS allocation indicatorfor all six repetitions would read “011011” for the example shown inFIG. 14 (removal), and “010101.” Again, the values of “0” and “1” may beswitched, in which case “1” would mean allocation of a DMRS to therespective TTI.

For example, the DMRS allocation indicator (e.g., the above describedone-bit or two-bit indicator for a respective TTI) may be included inhigher signaling. Accordingly, the DMRS allocation is signaledsemi-statically, particularly in RRC (Radio Resource Control) signaling.

In some embodiments, the control signaling further includes a DMRSactivation indicator which indicates whether or not no DMRS is allocatedto any of the one or more subsequent TTIs. Accordingly, the DMRSactivation indicator, which may be a one-bit indicator may indicatewhether flexible repetition configuration (allocation or non-allocationof DMRS to subsequent TTIs as well as the types of non-allocation) isapplied or not. In other words, the DMRS activation indicator is set fordeactivating or activating flexible DMRS configuration Moreover, thechoice of a particular DMRS activation indicator may indicate the degreeof flexibility in DMRS allocation.

In particular, the DMRS activating indicator may be a one-bit indicator,which indicates whether flexible DMRS is applied within a slot or even agreater time interval comprising several slots (e.g., the activationindicator may be semi-statically signaled, as will be described later).For instance, “0” indicates that flexible repetition allowingnon-allocation of DMRS to certain TTIs is not applied, and “1” indicatedthat flexible repetition is applied (or vice versa). The one-bitactivation indicator may be used in combination with respective two-bitindicators for the particular TTIs of a series of repetitions describesabove. For example, if the DMRS activation indicator indicates thatflexible indication is applied, the two-bit indicators may specifywhether DMRS allocation, DMRS removal or DMRS replacement is appliedwith respect to a particular TTI within a slot.

Alternatively, a one-bit activation indicator may indicate whether DMRSremoval or DMRS replacement is applied (e.g., “0” indicates removal and“1” indicates replacement). In this case, the or not the non-allocationof a DMRS (in particular the removal or replacement, depending on thevalue of the DMRS activation indicator) may be indicated by means of1-bit DMRS allocation indicators for the respective TTIs.

The activation indicator may be included in higher-layer signaling.Alternatively, the activation indicator may be included in downlinkcontrol information (DCI), which may be considered as dynamic signalingto carry e.g., scheduling information (grants) and/or transmissionparameters, i.e., in physical layer control signaling messagestransmitted on the PDCCH (Physical Downlink Control ChannelInformation). The present disclosure is not limited to a particular DCIformat, rather, the format may correspond to the existing/specified DCIformats for NR or could be agreed for particular service typed such asURLLC in the future. On the one hand, including the activation indicatorin the DCI provides greater flexibility as the activation/deactivationof flexible DMRS allocation can be performed with a grant for a sequenceof data repetitions. On the other hand, signaling the activationindicator in higher-layer signaling rather than DCI may avoidintroducing further DCI signaling and thus generating DCI signalingoverhead. However, if the DMRS allocator is to be included in the DCI,advantageously a one-bit allocation indicator is used.

The above described control signaling including DMRS allocationindicators for respective TTIs and the activation indicator constitute asignaling mechanism which can be embodied via RRC-signaling (semi-staticconfigurability) only. On the other hand, the signaling mechanism may beembodied to as a combination of both RRC and DCI signaling, as will bedescribed in the following.

If the configuration of the DMRS allocation/activation is performed onlyby means of RRC signaling, two bit fields, (referred to as “bit field 1”and “bit field 2” in this disclosure) may allow complete flexibility inallowing removal or replacement of DMRS symbols in any of the repetitionrounds, i.e., flexibly specifying in which order removal, replacement orallocation are respectively performed within sequences of repetitions.

The bit field 1 may be correspond to the above-described one-bitactivation indicator to indicate whether flexible repetitionconfiguration is applied or not. The exact repetition configuration(DMRS allocation) is configurable by bit field 2 corresponding to thetwo-bit allocation indicators being provided respectively for the TTIs.In bit field 2, the number of maximum bits will be two times the numberof maximum allowed repetitions. For example, if a maximum of sixrepetitions are allowed, then 12 bit field is defined in the RRC toallow flexible repetition configuration. Each repetition, i.e., eachsubsequent TTI is then associated with two bits having the indication aslisted above in the description of the DMRS allocation indicator.Accordingly, returning to the example of combination of DMRS removal andreplacement shown in FIG. 16, bit field 1 has value “1”—indication thatflexible repetition is applied, and bit field 2 takes the value “00 0110 00 01 10,” as described above and shown in FIG. 18.

As an alternative to bit field 1 being a 1 bit field and bit field twobeing a field of up to twelve bits, a one-bit bit activation indicatorindicating whether DMRS replacement or DMRS removal is applied may becombined with respective one-bit DMRS allocation indicator for thesubsequent TTIs described above. As a further alternative, a two-bitactivation indicator as described above may also be combined withrespective one-bit allocation indicators. In the latter signalingmechanisms, a bit field 2 of up to 12 bits may be reduced by half thebits to a field of up to six bits. Accordingly, resources in the RRCsignaling are saved.

Furthermore, in accordance with the present disclosure, signaling ofDMRS allocation(s) for the respective TTIs corresponding to repetitionscan also be performed without bit field 1. In particular, the controlsignaling relating to the DMRS allocation may only include the DMRSallocation indicators. However, if the activation indicator is includedin the RRC control signaling and indicates the value “0” (flexiblerepetition not applied), the bit field 2 need not be signaled in thesame RRC signaling, and the bits can be saved or reused for indicationsother than DMRS allocation.

As an alternative to control signaling of a DMRS allocation/activationin the RRC only, a signaling mechanism may include both RRC signalingand DCI signaling. Such embodiments may allow for a dynamic nature ofDMRS allocation to some degree.

In particular, the field referred to as “bit field 1” may be moved tothe DCI, i.e., a one-bit field corresponding to one of theabove-described one-bit activation indicators is added to the DCI todynamically signal whether flexible repetition configuration (which inthis case is still configurable by an RRC bit field) is applied (DCI bitfield value “1”) or not (value “0”). When control signaling in RRC andDCI are combined, the RRC bit field in the RRC signaling may be the sameas “bit field 2” describe above with respect to the usage of RRC only.Accordingly, the repetition configuration pattern (i.e., the respectiveDMRS allocations of the subsequent TTIs) is the same, but itsapplication (i.e., (de)activation, “switching” flexible DMRS allocationon or off) is dynamic is performed dynamically via DCI.

The one-bit field in the DCI may be the one-bit activation indicatorwhich specifies activation or deactivation of flexible DMRS allocation,as described above. In this case, the bit field in the RRC signaling maycorrespond to the two-bit DMRS allocation indicators as described above(up to twelve bits for up to six repetitions) which also indicatewhether DMRS symbol replacement or DMRS symbol removal is applied.However, the one-bit field in the DCI may also correspond to theabove-described indicator which indicates whether DMRS removal or DMRSreplacement is to be applied. In this case, the DMRS allocationindicator may have one bit per subsequent TTI, as described above (up tosix for up to six repetitions). As a further alternative, the type ofsymbol allocation in case no DMRS is allocated to a repetition(replacement or removal) may also be predefined, e.g., by a standard. Inthis case a one-bit activation indicator in the DCI and a one-bit DMRSallocation indicator per subsequent TTI (e.g., six bits corresponding tosix repetitions) is sufficient.

Further Embodiments

Some of the above embodiments have been described in particular withrespect to uplink transmissions/repetitions. However, as alreadymentioned, the present disclosure is not limited to the uplink case andmay also be used in association with PDSCH repetitions. Accordingly, insome embodiments, the transmission device rather than the receptiondevice corresponds to the gNB, The transmission generates a DMRSallocation indicator and optionally the activation indicator andtransmits control signaling including the allocation indicator to thereception device, i.e., the (user) terminal. The reception devicefurther receives the DMRS allocation indicator (and possibly theactivation indicator), and receives the data in the initial TTI, andreceives the DMRS in the subsequent TTIs in accordance with the DMRSallocation indicated by the received DMRS allocation indicator (andpossibly, the activation indicator). Herein, Activation indicator andallocation indicator may correspond to any of the indicators previouslydiscussed for the uplink case.

Furthermore, it should be noted that the present disclosure is directedat enabling flexibility in the time domain. The allocation of the dataand DMRS to carriers or subcarriers, i.e., resources in the frequencydomain of an OFDM system, or other resources such as spatial resources(beams), is not affected by DMRS allocation.

However, flexibility in repetition, as discussed in the presentdisclosure, can even be utilized in scenarios of frequency hopping, beamhopping and small measurement resources, as shown in FIGS. 19 to 21. Inorder to utilize the DMRS from last available transmission for channelestimation in current repetition round is that the same phase is used.For frequency hopping, the channel estimation from the last availableDMRS in the same hop can be done. Similarly for beam hopping, thechannel estimation from the last available DMRS in the same beam can bedone.

Accordingly, in some embodiments, as shown in FIG. 19, the transceiver,in operation, transmits the data allocated to a respective one of theone or more subsequent TTIs on a different set of subcarriers from theset of subcarriers in which the data has been transmitted in the TTIfrom among the plurality of TTIs directly preceding the respective TTI.In other words, in two TTIs from among the plurality of TTIs, the datais allocated to and transmitted on respectively different sets ofsubcarriers. The set of subcarriers may correspond to 12 subcarrierscorresponding to resource block size in frequency domain, or maycorrespond to a bandwidth part mentioned above. Accordingly, frequencyhopping can be performed preceding each subsequent TTI to which a DMRSis allocated. However, if frequency hopping is performed from one to thefollowing TTI from among the plurality of TTIs, the data in the TTIafter the frequency hopping step/operation is transmitted in a set ofsubcarriers on which a DMRS has been transmitted in one of the pluralityof TTIs previous to the TTI after the hopping step. In FIG. 19,frequency hopping between two respective groups/sets of frequencies isperformed. However, according to the present disclosure, hopping mayalso be performed between

Similarly to frequency hopping described above, in some embodiments, asshown in FIG. 20, the transceiver, in operation, transmits the dataallocated to a respective one of the one or more subsequent TTIs on abeam from the beam on which the data has been transmitted in the TTIfrom among the plurality of TTIs directly preceding the respectivesubsequent TTI. I.e., in two TTIs among the plurality of TTIs, the datais transmitted on respectively different beams. Similar to the case offrequency hopping, in each TTI, data is transmitted on a beam on whichthe data has previously been transmitted in another one of the pluralityof TTIs. In the example of beamhopping shown in FIG. 20, beamhoppingbetween two different beams is performed.

Beam changes or frequency changes from one to the next TTI may besignaled semi-statically. For instance, in addition to the DMRSallocation indicator, the RRC signaling may similarly include abeamhopping pattern indicator or a frequency hopping pattern indicator.Moreover, the DCI or RRC may include a beamhopping activator and/or afrequency hopping indicator. Alternatively, for the case that flexibleDMRS allocation is activated, predetermined hopping patterns may bedefined in a standard.

In some further embodiments, the plurality of TTIs to which the data isallocated to be transmitted in an initial transmission and repetitionsare not contiguous. I.e., there is a symbol between two from among theplurality of TTIs which is not comprised by any of the plurality ofTTIs. i.e., other data and or control signaling different from the datawhich is allocated to each of the plurality of TTIs may be allocated tothe symbol between two of the plurality of TTIs. An example is shown inFIG. 21, where, within a slot, there are an initial PUSCH transmissionand three data repetitions, and DMRS being allocated to the TTIscorresponding to the initial transmission and the second repetition.However, between each of these TTIs, there are symbols that are not usedfor the same series of initial transmission and repetitions. Moreover,these in-between symbols are symbols not used for uplink transmissions.

Furthermore, in most examples shown, the initial transmission beginswith a DMRS allocated to the first symbol of a slot. However,particularly in accordance with PUSCH mapping type B discussed above,the present disclosure is not limited to the initial TTI comprising thefirst symbol in the slot in time order. The initial transmission mayalternatively begin on a symbol other than the first symbol in a slot.

The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be partly or entirelyrealized by an LSI such as an integrated circuit, and each processdescribed in the each embodiment may be controlled partly or entirely bythe same LSI or a combination of LSIs. The LSI may be individuallyformed as chips, or one chip may be formed so as to include a part orall of the functional blocks. The LSI may include a data input andoutput coupled thereto. The LSI here may be referred to as an IC, asystem LSI, a super LSI, or an ultra LSI depending on a difference inthe degree of integration. However, the technique of implementing anintegrated circuit is not limited to the LSI and may be realized byusing a dedicated circuit, a general-purpose processor, or aspecial-purpose processor. In addition, a FPGA (Field Programmable GateArray) that can be programmed after the manufacture of the LSI or areconfigurable processor in which the connections and the settings ofcircuit cells disposed inside the LSI can be reconfigured may be used.The present disclosure can be realized as digital processing or analogueprocessing. If future integrated circuit technology replaces LSIs as aresult of the advancement of semiconductor technology or otherderivative technology, the functional blocks could be integrated usingthe future integrated circuit technology. Biotechnology can also beapplied.

According to one general aspect, the present disclosure providestransmission device for transmitting data to a reception device in acommunication system, the transmission device comprising circuitrywhich, in operation, allocates the data to a plurality of transmissiontime intervals, TTIs, respectively comprising a lower number of symbolsthan a slot and the plurality of TTIs including an initial TTI and oneor more subsequent TTIs subsequent to the initial TTI, wherein the dataallocated to each of the plurality of TTIs is the same, furtherallocates a demodulation reference signal, DMRS, to the initial TTI, andobtains a DMRS allocation for each of the subsequent TTIs indicatingwhether or not no DMRS is allocated to the respective TTI to betransmitted in addition to the data; and a transceiver which, inoperation, transmits, within the slot, the data and DMRS allocated tothe initial TTI and the data allocated to the one or more subsequentTTIs to the reception device, wherein DMRS transmission in the one ormore subsequent TTIs is performed in accordance with the DMRSallocation.

This facilitates providing greater flexibility for repetitions, andenabling latency reduction and/or reliability enhancement.

For instance, no DMRS is transmitted in at least one of the one or moresubsequent TTIs.

In some embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, a length of the respective TTIis reduced by one symbol corresponding to the DMRS.

This facilitates reducing latency.

In other embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, a symbol for allocation of theDMRS in the respective TTI is replaced by a symbol for allocation of thedata.

This facilitates enhancing reliability.

In further embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, either a length of therespective TTI is reduced by one symbol corresponding to the DMRS or asymbol for allocation of the DMRS in the respective TTI is replaced by asymbol for allocation of the data.

This enhances reducing latency and enhancing reliability.

For instance, if a symbol for allocation of the DMRS in the respectiveTTI is replaced by a symbol for allocation of the data, the data istransmitted in the respective TTI with a code rate lower than a coderate by which the data is transmitted in the initial TTI.

For instance, the transmission device transmits the data to thereception device on an uplink, the transceiver, in operation, furtherreceives, from the reception device, control signaling including a DMRSallocation indicator for each of the subsequent TTIs indicating therespective DMRS allocation, and the circuitry, in operation, obtains theDMRS allocation for each of the subsequent TTIs by evaluating thecontrol signaling.

For example, the DMRS allocation indicator for each subsequent TTI is atwo-bit allocation indicator.

In some embodiments, the DMRS allocation indicator is included inhigher-layer signaling.

For instance, the control signaling further includes an activationindicator indicating whether or not no DMRS is allocated to any of theone or more subsequent TTIs.

In some exemplary embodiments, the activation indicator is included inhigher-layer signaling. This provides for avoiding additional physicallayer signaling overhead.

In other exemplary embodiments, the activation indicator is a one-bitindicator included in downlink channel information, DCI.

This enables dynamic switching of flexible DMRS allocation.

In some embodiments, the transmission device transmits the data to thereception device on a downlink, and the transceiver, in operation,further transmits, to the reception device, control signaling includinga DMRS allocation indicator for each of the subsequent TTIs indicatingthe respective DMRS allocation.

For instance, in two TTIs from among the plurality of TTIs, the data isallocated to and transmitted on respectively different sets ofsubcarriers.

For example, in two TTIs from among the plurality of TTIs, the data istransmitted on respectively different beams.

In some embodiments, a symbol between two from among the plurality ofTTIs is not comprised by any of the plurality of TTIs.

According to another general aspect, provided is a reception device forreceiving data from a transmission device in a communication system, thereception device comprising circuitry which, in operation, obtains ademodulation reference signal, DMRS, allocation for each of one or moresubsequent TTIs subsequent to an initial TTI, the DMRS allocationindicating whether or not no DMRS is allocated to the respective TTI tobe received in addition to the data, wherein a plurality of TTIsincluding the initial TTI and the one or more subsequent TTIsrespectively comprise a lower number of symbols than a slot, a DMRS isallocated to the initial TTI, and the data allocated each of theplurality of TTIs is the same and further comprising a transceiverwhich, in operation, receives, within the slot, the data and DMRSallocated to the initial TTI and the data allocated to the one or moresubsequent TTIs from the transmission device, wherein DMRS reception inthe one or more subsequent TTIs is performed in accordance with the DMRSallocation.

For instance, no DMRS is transmitted in at least one of the one or moresubsequent TTIs.

In some embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, a length of the respective TTIis reduced by one symbol corresponding to the DMRS.

In other embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, a symbol for allocation of theDMRS in the respective TTI is replaced by a symbol for allocation of thedata.

In further embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, either a length of therespective TTI is reduced by one symbol corresponding to the DMRS or asymbol for allocation of the DMRS in the respective TTI is replaced by asymbol for allocation of the data.

For instance, if a symbol for allocation of the DMRS in the respectiveTTI is replaced by a symbol for allocation of the data, the data istransmitted in the respective TTI with a code rate lower than a coderate by which the data is transmitted in the initial TTI.

For instance, the reception device receives the data from thetransmission device on an uplink, further transmits, to the transmissiondevice, control signaling including a DMRS allocation indicator for eachof the subsequent TTIs indicating the respective DMRS allocation.

For example, the DMRS allocation indicator for each subsequent TTI is atwo-bit allocation indicator.

In some embodiments, the DMRS allocation indicator is included inhigher-layer signaling.

For instance, the control signaling further includes an activationindicator indicating whether or not no DMRS is allocated to any of theone or more subsequent TTIs.

In some exemplary embodiments, the activation indicator is included inhigher-layer signaling.

In other exemplary embodiments, the activation indicator is a one-bitindicator included in downlink channel information, DCI.

In some embodiments, the reception device receives the data from thetransmission device on a downlink, the transceiver, in operation,further receives, from the transmission device, control signalingincluding a DMRS allocation indicator for each of the subsequent TTIsindicating the respective DMRS allocation, and the circuitry, inoperation, obtains the DMRS allocation for each of the subsequent TTIsby evaluating the control signaling.

For instance, in two TTIs from among the plurality of TTIs, the data isallocated to and received on respectively different sets of subcarriers.

For example, in two TTIs from among the plurality of TTIs, the data isreceived on respectively different beams.

In some embodiments, a symbol between two from among the plurality ofTTIs is not comprised by any of the plurality of TTIs.

In another general aspect, the disclosure provides a transmission methodfor a transmission device transmitting data to a reception device in acommunication system, the transmission method comprising obtaining ademodulation reference signal, DMRS, allocation for each of one or moresubsequent TTIs subsequent to an initial TTI, the DMRS allocationindicating whether or not no DMRS is allocated to the respective TTI tobe transmitted in addition to the data, wherein a plurality of TTIsincluding the initial TTI and the one or more subsequent TTIsrespectively comprise a lower number of symbols than a slot; allocatingthe same data to each of the plurality of TTIs, and allocating a DMRS tothe initial TTI; and transmitting, within the slot, the data and DMRSallocated to the initial TTI and the data allocated to the one or moresubsequent TTIs to the reception device, wherein DMRS transmission inthe one or more subsequent TTIs is performed in accordance with the DMRSallocation.

For instance, no DMRS is transmitted in at least one of the one or moresubsequent TTIs.

In some embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, a length of the respective TTIis reduced by one symbol corresponding to the DMRS.

In other embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, a symbol for allocation of theDMRS in the respective TTI is replaced by a symbol for allocation of thedata.

In further embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, either a length of therespective TTI is reduced by one symbol corresponding to the DMRS or asymbol for allocation of the DMRS in the respective TTI is replaced by asymbol for allocation of the data.

For instance, if a symbol for allocation of the DMRS in the respectiveTTI is replaced by a symbol for allocation of the data, the data istransmitted in the respective TTI with a code rate lower than a coderate by which the data is transmitted in the initial TTI.

For instance, the data is transmitted to the reception device on anuplink, the transmission method further comprises receiving, from thereception device, control signaling including a DMRS allocationindicator for each of the subsequent TTIs indicating the respective DMRSallocation, and in the obtaining step, the DMRS allocation is obtainedfor each of the subsequent TTIs by evaluating the control signaling.

For example, the DMRS allocation indicator for each subsequent TTI is atwo-bit allocation indicator.

In some embodiments, the DMRS allocation indicator is included inhigher-layer signaling.

For instance, the control signaling further includes an activationindicator indicating whether or not no DMRS is allocated to any of theone or more subsequent TTIs.

In some exemplary embodiments, the activation indicator is included inhigher-layer signaling.

In other exemplary embodiments, the activation indicator is a one-bitindicator included in downlink channel information, DCI.

In some embodiments, the data is transmitted to the reception device ona downlink, and the transmission method further comprises transmitting,to the reception device, control signaling including a DMRS allocationindicator for each of the subsequent TTIs indicating the respective DMRSallocation.

For instance, in two TTIs from among the plurality of TTIs, the data isallocated to and transmitted on respectively different sets ofsubcarriers.

For example, in two TTIs from among the plurality of TTIs, the data istransmitted on respectively different beams.

In some embodiments, a symbol between two from among the plurality ofTTIs is not comprised by any of the plurality of TTIs.

According to another general aspect, the disclosure provides a receptionmethod for a reception device receiving data from a transmission devicein a communication system, the reception method comprising obtaining ademodulation reference signal, DMRS, allocation for each of one or moresubsequent TTIs subsequent to an initial TTI, the DMRS allocationindicating whether or not no DMRS is allocated to the respective TTI tobe received in addition to the data, wherein a plurality of TTIsincluding the initial TTI and the one or more subsequent TTIsrespectively comprise a lower number of symbols than a slot, a DMRS isallocated to the initial TTI, and the data allocated each of theplurality of TTIs is the same, and receiving, within the slot, the dataand DMRS allocated to the initial TTI and the data allocated to the oneor more subsequent TTIs from the transmission device, wherein DMRSreception in the one or more subsequent TTIs is performed in accordancewith the DMRS allocation.

For instance, no DMRS is transmitted in at least one of the one or moresubsequent TTIs.

In some embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, a length of the respective TTIis reduced by one symbol corresponding to the DMRS.

In other embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, a symbol for allocation of theDMRS in the respective TTI is replaced by a symbol for allocation of thedata.

In further embodiments, the DMRS allocation further indicates that if noDMRS is allocated to the respective TTI, either a length of therespective TTI is reduced by one symbol corresponding to the DMRS or asymbol for allocation of the DMRS in the respective TTI is replaced by asymbol for allocation of the data.

For instance, if a symbol for allocation of the DMRS in the respectiveTTI is replaced by a symbol for allocation of the data, the data istransmitted in the respective TTI with a code rate lower than a coderate by which the data is transmitted in the initial TTI.

For instance, the data is received from the transmission device on anuplink, and the method further comprises transmitting, to thetransmission device, control signaling including a DMRS allocationindicator for each of the subsequent TTIs indicating the respective DMRSallocation.

For example, the DMRS allocation indicator for each subsequent TTI is atwo-bit allocation indicator.

In some embodiments, the DMRS allocation indicator is included inhigher-layer signaling.

For instance, the control signaling further includes an activationindicator indicating whether or not no DMRS is allocated to any of theone or more subsequent TTIs.

In some exemplary embodiments, the activation indicator is included inhigher-layer signaling.

In other exemplary embodiments, the activation indicator is a one-bitindicator included in downlink channel information, DCI.

In some embodiments, the data is received from the transmission deviceon a downlink, the reception method further includes receiving, from thetransmission device, control signaling including a DMRS allocationindicator for each of the subsequent TTIs indicating the respective DMRSallocation, and in the obtaining step, the DMRS allocation for each ofthe subsequent TTIs is obtained by evaluating the control signaling.

For instance, in two TTIs from among the plurality of TTIs, the data isallocated to and received on respectively different sets of subcarriers.

For example, in two TTIs from among the plurality of TTIs, the data isreceived on respectively different beams.

In some embodiments, a symbol between two from among the plurality ofTTIs is not comprised by any of the plurality of TTIs.

Summarizing, the disclosure relates to a transmission device fortransmitting data to a reception device in a communication system. Thetransmission device comprises circuitry which, in operation, allocatesthe data to a plurality of transmission time intervals, TTIs,respectively comprising a lower number of symbols than a slot and theplurality of TTIs including an initial TTI and one or more subsequentTTIs subsequent to the initial TTI, wherein the data allocated to eachof the plurality of TTIs is the same, further allocates a demodulationreference signal, DMRS, to the initial TTI, and obtains a DMRSallocation for each of the subsequent TTIs indicating whether or not noDMRS is allocated to the respective TTI to be transmitted in addition tothe data. The transmission device further comprises a transceiver which,in operation, transmits, within the slot, the data and DMRS inaccordance with the DMRS allocation.

1. A transmission device for transmitting data to a reception device ina communication system, the transmission device comprising: circuitrywhich, in operation, allocates the data to a plurality of transmissiontime intervals, TTIs, respectively comprising a lower number of symbolsthan a slot and the plurality of TTIs including an initial TTI and oneor more subsequent TTIs subsequent to the initial TTI, wherein the dataallocated to each of the plurality of TTIs is the same, furtherallocates a demodulation reference signal, DMRS, to the initial TTI, andobtains a DMRS allocation for each of the subsequent TTIs indicatingwhether or not no DMRS is allocated to the respective TTI to betransmitted in addition to the data; and a transceiver which, inoperation, transmits, within the slot, the data and DMRS allocated tothe initial TTI and the data allocated to the one or more subsequentTTIs to the reception device, wherein DMRS transmission in the one ormore subsequent TTIs is performed in accordance with the DMRSallocation.
 2. The transmission device according to claim 1, wherein noDMRS is transmitted in at least one of the one or more subsequent TTIs.3. The transmission device according to claim 1, wherein the DMRSallocation further indicates that if no DMRS is allocated to therespective TTI, a length of the respective TTI is reduced by one symbolcorresponding to the DMRS.
 4. The transmission device according to claim1, wherein the DMRS allocation further indicates that if no DMRS isallocated to the respective TTI, a symbol for allocation of the DMRS inthe respective TTI is replaced by a symbol for allocation of the data.5. The transmission device according to claim 1, wherein the DMRSallocation further indicates that if no DMRS is allocated to therespective TTI, either a length of the respective TTI is reduced by onesymbol corresponding to the DMRS or a symbol for allocation of the DMRSin the respective TTI is replaced by a symbol for allocation of thedata.
 6. The transmission device according to claim 4, wherein, if asymbol for allocation of the DMRS in the respective TTI is replaced by asymbol for allocation of the data, the data is transmitted in therespective TTI with a code rate lower than a code rate by which the datais transmitted in the initial TTI.
 7. The transmission device accordingto claim 1, wherein the transmission device transmits the data to thereception device on an uplink, the transceiver, in operation, furtherreceives, from the reception device, control signaling including a DMRSallocation indicator for each of the subsequent TTIs indicating therespective DMRS allocation, and the circuitry, in operation, obtains theDMRS allocation for each of the subsequent TTIs by evaluating thecontrol signaling.
 8. The transmission device according to claim 7,wherein the DMRS allocation indicator for each subsequent TTI is atwo-bit allocation indicator.
 9. The transmission device according toclaim 7, wherein the DMRS allocation indicator is included inhigher-layer signaling.
 10. The transmission device according to claim7, wherein the control signaling further includes an activationindicator indicating whether or not no DMRS is allocated to any of theone or more subsequent TTIs.
 11. The transmission device according toclaim 10, wherein the activation indicator is included in higher-layersignaling.
 12. The transmission device according to claim 10, whereinthe activation indicator is a one-bit indicator included in downlinkchannel information, DCI.
 13. A reception device for receiving data froma transmission device in a communication system, the reception devicecomprising: circuitry which, in operation, obtains a demodulationreference signal, DMRS, allocation for each of one or more subsequentTTIs subsequent to an initial TTI, the DMRS allocation indicatingwhether or not no DMRS is allocated to the respective TTI to be receivedin addition to the data, wherein a plurality of TTIs including theinitial TTI and the one or more subsequent TTIs respectively comprise alower number of symbols than a slot, a DMRS is allocated to the initialTTI, and the data allocated each of the plurality of TTIs is the same;and a transceiver which, in operation, receives, within the slot, thedata and DMRS allocated to the initial TTI and the data allocated to theone or more subsequent TTIs from the transmission device, wherein DMRSreception in the one or more subsequent TTIs is performed in accordancewith the DMRS allocation.
 14. A transmission method for a transmissiondevice transmitting data to a reception device in a communicationsystem, the transmission method comprising: obtaining a demodulationreference signal, DMRS, allocation for each of one or more subsequentTTIs subsequent to an initial TTI, the DMRS allocation indicatingwhether or not no DMRS is allocated to the respective TTI to betransmitted in addition to the data, wherein a plurality of TTIsincluding the initial TTI and the one or more subsequent TTIsrespectively comprise a lower number of symbols than a slot; allocatingthe same data to each of the plurality of TTIs, and allocating a DMRS tothe initial TTI; and transmitting, within the slot, the data and DMRSallocated to the initial TTI and the data allocated to the one or moresubsequent TTIs to the reception device, wherein DMRS transmission inthe one or more subsequent TTIs is performed in accordance with the DMRSallocation.
 15. A reception method for a reception device receiving datafrom a transmission device in a communication system, the receptionmethod comprising: obtaining a demodulation reference signal, DMRS,allocation for each of one or more subsequent TTIs subsequent to aninitial TTI, the DMRS allocation indicating whether or not no DMRS isallocated to the respective TTI to be received in addition to the data,wherein a plurality of TTIs including the initial TTI and the one ormore subsequent TTIs respectively comprise a lower number of symbolsthan a slot, a DMRS is allocated to the initial TTI, and the dataallocated each of the plurality of TTIs is the same; and receiving,within the slot, the data and DMRS allocated to the initial TTI and thedata allocated to the one or more subsequent TTIs from the transmissiondevice, wherein DMRS reception in the one or more subsequent TTIs isperformed in accordance with the DMRS allocation.